JP2007074787A - Driver and driving method of oscillatory actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driver and a driving method of an oscillatory actuator in which the occurrence of various kinds of faults can be prevented as much as possible when the drive control of the oscillatory actuator is performed from a low speed rotation zone to a high speed rotation zone. <P>SOLUTION: When the target speed of an ultrasonic motor is low and the ultrasonic motor is rotated at a low speed, drive control and intermittent drive control are performed by a rate multiplier system for generating a drive pulse digitally. When the target speed of the ultrasonic motor is high and the ultrasonic motor is rotated at a high speed, drive control and continuous drive control are performed by a VCO system for generating a drive pulse in analog. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a driving device and a driving method for a vibration actuator, and more particularly to a technique for sweeping the frequency of a driving signal.

  In recent years, an ultrasonic motor has been put into practical use as a type of vibration actuator that obtains a rotational force or a linear propulsive force by using a traveling wave generated by mechanical vibration of an electro-mechanical energy conversion element. This ultrasonic motor provides high torque at low speed, can be driven directly without the need for a gear reduction mechanism, has excellent responsiveness and controllability, and can be positioned very finely. There is a feature such as having. For this reason, the ultrasonic motor is used for automatic focusing of a camera, paper conveyance of a copying machine, rotation of a photosensitive drum, rotation of a monitoring camera, and the like.

  FIG. 9 is a schematic diagram for explaining an outline of drive control of the ultrasonic motor. The ultrasonic motor 30 includes a vibrating body 31, a stator 32, a rotor 33, a rotating shaft 34, and a rib 39. The vibrating body 31 is an electro-mechanical energy conversion element, and a piezoelectric element is used. The stator 32 is a member that amplifies a vibration wave (traveling wave) generated by the vibrating body 31 and transmits the amplified wave to the rotor 33. One surface of the stator 32 is bonded to the vibrating body 31, and the other surface is pressed against the rotor 33 through very thin ribs 39 attached to the surface of the rotor 33.

  Under such a configuration, when a specific high frequency voltage is applied to the vibrating body 31, the vibrating body 31 resonates and generates ultrasonic vibrations. The ultrasonic vibration is a traveling wave that continuously travels in one direction while bending the stator 32, and is transmitted to the rotor 33 through the rib 39. At this time, an elliptical motion that draws a trajectory in the opposite direction to the traveling wave occurs at the apex portion of the traveling wave. As a result, the rotor 33 (rib 39) rotates in the direction opposite to the traveling direction of the traveling wave.

  In FIG. 9, the control circuit 27 generates an A phase signal and a B phase signal as drive signals having a drive frequency corresponding to the target speed of the ultrasonic motor 30. The A-phase signal and the B-phase signal are drive signals having the same pulse waveform having the same frequency and a phase difference of 90 degrees. These A-phase signal and B-phase signal are voltage amplified by the voltage amplification circuit 28, shaped into a sine wave by the coil 29, and supplied to the vibrating body 31 of the ultrasonic motor 30.

  The control circuit 27 generates drive signals related to the A phase signal and the B phase signal by the following method. FIG. 10 is a diagram showing the relationship between the driving frequency and the rotation speed of the ultrasonic motor 30. In FIG. 10, the X axis is the driving frequency of the A phase signal and the B phase signal, and the Y axis is the rotational speed of the ultrasonic motor.

  In the example of FIG. 10, the driving frequency for obtaining a rotational speed of 720 ° / second is 35 KHz, and the driving frequency for obtaining a rotational speed of 60 ° / second is 38 KHz. That is, the rotation speed increases as the drive frequency decreases.

  Therefore, the control circuit 27 drives the ultrasonic motor 30 at a desired rotation speed by sweeping the drive frequency from a high frequency to a low frequency. For example, when driving at 720 ° / second, the control circuit 27 performs sweeping of the drive frequency from an initial frequency of 39 KHz to a frequency of 35 KHz so as to obtain a rotation speed of 720 ° / second. Further, when rotating at 60 ° / second, the control circuit 27 performs control so as to obtain a rotational speed of 60 ° / second by gradually sweeping the drive frequency from the initial frequency of 44 KHz to the frequency of 38 KHz.

  By the way, if the ultrasonic motor 30 is continuously driven in the low speed rotation range, a problem arises in durability as compared with the case of driving in the high speed rotation range. That is, the major factor determining the durability of the ultrasonic motor is the surface wear of the stator 32 in contact with the rib 39, and the portion in contact with the rib 39 is scraped by about 2 microns due to wear. As a result, the torque of the ultrasonic motor 30 is suddenly reduced, and the life of the motor is exhausted.

  FIGS. 11A and 11B show surface vibrations of the stator 32 when rotating at a high speed and when rotating at a low speed, respectively. Reference numeral 41 shown in FIG. 11A denotes the surface of the stator 32, and mechanical vibration waves are traveling. Reference numeral 40 denotes a surface of the rib 39 attached to the rotor 33. As shown in FIG. 11A, during high speed rotation, the amplitude of the traveling wave traveling on the stator 32 is large, so that the contact area with the surface 40 of the rib 39 is small as indicated by 42. For this reason, at the time of high speed rotation, even if the amount of rotation is large, the amount of wear of the stator 32 is small.

  Reference numeral 43 shown in FIG. 11B denotes the surface of the stator 32, and mechanical vibration waves are traveling. Reference numeral 44 denotes a surface of the rib 39 attached to the rotor 33. As shown in FIG. 11B, during low-speed rotation, the amplitude of the traveling wave traveling on the stator 32 is small, so that the contact area with the surface 40 of the rib 39 is large as indicated by 45. For this reason, during low-speed rotation, the amount of wear of the stator 32 when the rotation amount is the same as during high-speed rotation is greater than during high-speed rotation, and the life of the ultrasonic motor 30 is shortened.

  Further, when the ultrasonic motor 30 is rotated at a very low speed, the torque is small and unstable. In order to solve this problem, an intermittent driving method is also realized in which a driving pattern is repeated in which driving is temporarily stopped after a certain period of time and then restarted after a predetermined time (Japanese Patent Laid-Open No. 05-336762). See the official gazette).

Further, as a driving method for the ultrasonic motor 30, a VCO (Voltage Controlled Oscillator) method for instructing the sweeping driving frequency in an analog manner and a rate multiplier method for digitally instructing a driving frequency for sweeping are realized ( JP-A-11-341841 and JP-A-2000-184762).
JP 05-336762 A Japanese Patent Application Laid-Open No. 11-341841 JP 2000-184762 A

  However, in the VCO method, when the drive control is performed from the low speed rotation range to the high speed rotation range, the range in which the drive frequency is changed becomes wide. For this reason, the control resolution is lowered, and particularly when the ultrasonic motor is rotated at a high speed, the rotational speed of the ultrasonic motor becomes unstable and noise is increased.

  On the other hand, the rate multiplier method generates an audible sound due to beats in order to change the drive frequency in small increments. In the case of high-speed rotation, the analog VCO method that indicates the drive frequency is more advantageous than the rate multiplier method that digitally indicates the drive frequency in order to prevent noise.

  In addition, the intermittent drive system can ensure the stability of the torque even during low-speed rotation, but the above-mentioned Patent Document 1 discloses a specific method of intermittent drive control according to the required rotational speed. Not.

  Accordingly, the present invention provides a drive device and a drive method for a vibration type actuator that can prevent the occurrence of various problems as much as possible when driving the vibration type actuator from a low speed rotation range to a high speed rotation range. With the goal.

  In order to solve the above problems, the present invention is a vibration type having a drive control means for changing the motion speed of a movable body to which the vibration of the vibration body is transmitted by sweeping the frequency of the drive signal supplied to the vibration body. In the actuator drive device, the drive control means has a selection means for controlling a plurality of drive means and selecting one or more drive means from the plurality of drive means.

  According to the present invention, for example, based on the target motion speed of the movable body, the frequency band of the drive signal, etc., one or more drive means are selected from a plurality of drive means and the drive is supplied to the vibrator The frequency of the signal can be swept.

  Therefore, when driving the vibration type actuator from the low-speed rotation range to the high-speed rotation range, for example, vibration that can prevent as much as possible the occurrence of various problems such as reduced life, instability in motion, and generation of drive sound. It is possible to provide a driving device and a driving method for a mold actuator.

[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of a drive control unit of a vibration type actuator (ultrasonic motor) in the first to third embodiments of the present invention. In the motor control circuit 230 shown in FIG. 1, the drive frequency of the ultrasonic motor 30 is swept from the initial frequency on the high frequency side to the low frequency direction by feedback control, and the ultrasonic motor 30 is controlled to rotate at the target speed. ing.

  In the present embodiment, it is assumed that the structure of the ultrasonic motor 30 is the same as that shown in FIG. 9, but the present embodiment also applies to ultrasonic motors having other structures. Such motor drive control can be applied (the same applies to the second and third embodiments). In addition, the ultrasonic motor 30 in the present embodiment is assumed to be used as a vibration type actuator for rotational driving, but the ultrasonic motor or the like as a vibration type actuator for linear reciprocating driving is used in this embodiment. Such motor drive control can also be applied (the same applies to the second and third embodiments).

  In FIG. 1, the CPU 231 generally controls the apparatus on which the ultrasonic motor 30 is mounted, and when the ultrasonic motor 30 is rotationally driven, a target speed (target rotational speed: target motion speed), a reference speed ( Information (hereinafter referred to as parameters) such as reference rotation speed (reference movement speed), rotation amount (target position), drive pulse width and initial frequency (cycle) is output to the motor control circuit 230. In the first embodiment, the motor control circuit 230 controls the drive of the ultrasonic motor 30 by selecting the rate multiplier method or the VCO method according to the target speed given from the CPU 231.

  The CPU 231 has a timer 233 built therein. As will be described later, the timer 233 is used to change the initial frequency of the drive pulse as necessary when the ultrasonic motor 30 is driven by the rate multiplier method. A CPG (Clock Pulse Generator) 232 generates a clock pulse and supplies it to the motor control circuit 230. Each part of the motor control circuit 230 performs its own operation in synchronization with a clock pulse in order to perform motor drive control in a harmonious manner as a whole.

  Next, each part of the motor control circuit 230 will be described. The parameter storage unit 234 stores the above parameters received from the CPU 231. Among these parameters, the reference speed is transmitted to the speed comparison unit 220, the period related to the initial frequency is transmitted to the drive period setting unit 222, and the target speed and the pulse width are transmitted to the drive signal generation circuit 223. The reference speed is a speed set based on the target speed. In the case of continuous drive control, the reference speed = target speed, and in the case of intermittent drive control, the reference speed> target speed. Details of these will be described later.

  The speed comparison unit 220 compares the above-described reference speed with an actual speed of the ultrasonic motor 30 output from the speed calculation unit 227 described later, and a speed deviation that is the difference, that is, a value of (reference speed−actual speed). Is output to the integrator 221. When the actual speed is much smaller than the reference speed, the speed deviation is a large positive value, and the drive frequency is swept greatly in the low frequency direction. Further, when the actual speed is slightly smaller than the reference speed, the speed deviation becomes a small plus value, and the drive frequency is swept smaller in the low frequency direction. When the actual speed is higher than the reference speed, the speed deviation is a negative value, and the drive frequency is swept in the high frequency direction.

  The integrator 221 integrates the speed deviation input from the speed comparison unit 220 over time in order to smoothly accelerate or decelerate the rotation speed of the ultrasonic motor 30. The time interval at which the integrator 221 performs integration is specified by the integration gain stored in the parameter storage unit 234. When the value of the integral gain is large, the frequency of integration by the integrator 221 decreases, and the acceleration / deceleration of the rotational speed of the ultrasonic motor 30 becomes smooth. On the other hand, when the value of the integral gain is small, the frequency of integration by the integrator 221 increases, and the acceleration / deceleration of the rotational speed of the ultrasonic motor 30 becomes steep.

  The drive cycle setting unit 222 adds the speed deviation integrated by the integrator 221 to the cycle related to the initial frequency, and outputs the added value to the drive signal generation circuit 223 as new drive cycle data Tx.

  In the present embodiment, drive control is performed using a cycle (cycle = 1 / frequency). However, drive control can also be performed using a frequency instead of a cycle. In the present embodiment, the speed deviation from the speed comparison unit 220 is processed only by the integrator 221, but a known component composed of three components of P (Proportional), I (Integral), and D (Differential). Like PID control, it is also possible to process the speed deviation by proportional gain or differential gain (the same applies to the second and third embodiments).

  The drive signal generation circuit 223 generates a drive pulse for driving the ultrasonic motor 30 based on the drive cycle data Tx output from the drive cycle setting unit 222, the pulse width supplied from the CPU 231, and the like. Note that the drive signal generation circuit 223 according to the present embodiment is configured to generate drive pulses by two methods of a VCO method and a rate multiplier method, as will be described later (second embodiment). The same).

  The voltage amplification circuit 28 amplifies the voltage of the drive pulse output from the drive signal generation circuit 223. The coil 29 converts the drive pulse voltage-amplified by the voltage amplification circuit 28 into a sine wave and supplies the sine wave to the vibrating body 31 of the ultrasonic motor 30. The encoder 224 is a sensor for detecting the rotational speed of the ultrasonic motor 30 and outputs a detection pulse having a frequency corresponding to the rotational speed of the ultrasonic motor 30.

  The detection pulse from the encoder 224 is supplied to the speed calculation unit 227. The speed calculation unit 227 calculates an actual speed based on the detected pulse and feeds back to the speed comparison unit 220. The motor control circuit 230 performs such feedback control, and repeats the process of generating a new drive pulse corresponding to the speed difference between the reference speed and the actual speed. Thereby, the drive frequency of the ultrasonic motor 30 is swept in the direction of the drive frequency related to the target speed (reference speed).

  Next, a detailed configuration of the drive signal generation circuit 223 according to the first embodiment will be described with reference to FIG.

  When the ultrasonic motor 30 is driven, the driving method selection unit 130 acquires the target speed from the parameter storage unit 234 and generates a driving pulse by the VCO method according to the target speed, or by the rate multiplier method. Decide whether to generate drive pulses. In the present embodiment, drive method selection section 130 outputs a signal of logic “0” when the target speed is 120 ° / second or more. This logic “0” signal is supplied to the gate 138 as it is, and inverted to the gate 133 by the inverter 131 to be supplied as a “1” signal. Therefore, when the target speed is 120 ° / second or more, the gate 133 is opened, and the driving cycle data Tx from the driving cycle setting unit 222 is sent to the VCO value calculation unit 134 via the gate 133. It becomes.

  On the other hand, when the target speed is less than 120 ° / second, the driving method selection unit 130 outputs a signal of logic “1”. This logic “1” signal is supplied to the gate 138 as it is, and is inverted by the inverter 131 and supplied to the gate 133 as a “0” signal. Accordingly, when the target speed is 120 ° / second or more, the gate 138 is opened, and the driving cycle data Tx from the driving cycle setting unit 222 is sent to the rate multiplier system 16-bit register 139 via the gate 138. Will be.

である。 Next, the VCO circuit block will be described. The VCO value calculation unit 134 calculates a digital value corresponding to the analog voltage level of the input drive cycle data Tx.
This formula is

It is.

  However, Dvco is a VCO value as a digital value of a calculation result, Tx is input drive cycle data, Tmax is a maximum cycle that can be set by the VCO circuit 137, and Tmin is a minimum cycle that can be set by the VCO circuit 137. K1 is the maximum value (1023) of the period that can be specified by the 10-bit register 135.

  In this embodiment, the setting range of the drive frequency is adjusted to be 40 KHz (Tmin = 25 μS) to 33 KHz (Tmax = 30.3 μS). A method for adjusting Tmin and Tmax will be described later. For example, when the drive cycle data Tx is 25.64 μS (39 KHz), Dvco is calculated as (25.64-25) / (30.3-25) × 1023 = 120 according to the above formula 1.

  Tmax and Tmin are adjusted when a VCO measurement instruction is received from the CPU 231. That is, when receiving the VCO measurement instruction from the CPU 231, the VCO value calculation unit 134 first outputs the value of K 1, that is, “1023”, which is the maximum value of the period that can be specified by the 10-bit register 135, to the VCO circuit 137. . Then, the VCO value calculation unit 134 receives the pulse period corresponding to “1023” from the VCO circuit 137, and stores the value obtained by digitally converting the pulse period as Tmax. Next, the VCO value calculation unit 134 outputs “0” to the VCO circuit 137, receives the pulse cycle corresponding to this “0” from the VCO circuit 137, and sets the value obtained by digitally converting the pulse cycle as Tmin. Remember.

  The above-mentioned VCO measurement instruction is given from the CPU 231 when the apparatus equipped with the ultrasonic motor 30 is reset. Further, the pulse periods (Tmax, Tmin: drive frequency ranges) respectively corresponding to “1023” and “0” are set by a resistor 147 or the like, as will be described later.

  The 10-bit register 135 stores the VCO value Dvco calculated by the VCO value calculation unit 134. As described above, the 10-bit register 135 can store the VCO value Dvco as a digital value from “0” to “1023”. In the present embodiment, considering the storage capacity of the 10-bit register 135, the value of K1 used in the VCO value setting unit 134 is defined as “1023”.

  The DA conversion circuit 136 converts the digital VCO value stored in the 10-bit register 135 into an analog voltage level. The analog voltage level increases as the VCO value increases, and the analog voltage level decreases as the VCO value decreases. For example, when the VCO value is “120”, the analog voltage level output from the DA conversion circuit 136 is 1V + 120/1023 = about 1.117V.

  The VCO circuit 137 is a circuit that outputs a drive pulse having a cycle corresponding to the analog voltage level from the DA converter circuit 136 within a range of Tmax and Tmin preset by the resistor 147 and the like. For example, when the analog voltage level is 1.117 V, the VCO circuit 137 outputs a drive pulse having a period of 25.64 μS (39 KHz). The cycle of 25.64 μS is the same as the drive cycle data Tx output from the drive cycle setting unit 222. In other words, the VCO circuit 137 outputs a drive pulse having the same cycle as the drive cycle data Tx output from the drive cycle setting unit 222.

  The range of the period (frequency) of the drive pulse output from the VCO circuit 137 is set by the resistor 147, the variable resistor 146, and the capacitor 145. For example, when the resistance value of the resistor 147 is increased, the frequency range of the drive pulse signal is narrowed, and when the resistance value is decreased, the frequency range of the drive pulse is expanded. Specifically, for example, when the resistance value of the resistor 147 is set to 15 KΩ, the variable frequency range of the VCO circuit 137 becomes 12 KHz, and the VCO circuit 137 can output drive pulses having a frequency from 33 KHz to 45 KHz. Further, when the resistance value of the resistor 147 is set to 22 KΩ, the variable frequency range of the VCO circuit 137 becomes 7 KHz, and the VCO circuit 137 can output drive pulses having a frequency from 33 KHz to 40 KHz.

  Thus, the resolution of the drive control of the ultrasonic motor 30 by the VCO circuit 137 is determined by the variable frequency range set by the resistor 147. For example, the resolution of the drive control is 12 KHz / 1024 = 11.7 Hz when the resistance value of the resistor 147 is 15 KΩ. When the resistance value of the resistor 147 is 22 KHz, the resolution of the drive control is 7 KHz / 1024 = 6.8 Hz. That is, the resolution of the drive control of the ultrasonic motor 30 by the VCO circuit 137 decreases when the resistance value of the resistor 147 is decreased, and increases when the resistance value of the resistor 147 is increased.

  Therefore, in the present embodiment, the resistance value of the resistor 147 is set to 22 KΩ in order to increase the resolution of drive control of the ultrasonic motor 30. As described above, by increasing the resolution of drive control of the ultrasonic motor 30, the ultrasonic motor 30 can be stably driven even during high-speed rotation.

  In order to increase the resolution of the drive control of the ultrasonic motor 30, a method of increasing the number of bits of the 10-bit register 135 to 12 bits or 16 bits is also conceivable. Since the resolution of the output analog voltage is 1 mV or less, it is not appropriate as a method for improving the resolution of drive control of the ultrasonic motor 30.

  Further, by changing the capacitance of the capacitor 145 or changing the resistance value of the variable resistor 146, the maximum cycle Tmax and the minimum cycle Tmin that can be set by the VCO circuit 137, that is, the variable frequency range of the VCO circuit 137, And the resolution can be changed. Therefore, in the present embodiment, a capacitor having a predetermined capacitance is used as the capacitor 145, and the resistance value of the resistor 147 is fixed to 22 KHz for the above-described reason, and then the resistance value of the variable resistor 146 is set. By changing the frequency, the frequency corresponding to the period of Tmax and Tmin is adjusted to 33 KHz and 40 KHz (see reference numeral 210 in FIG. 3).

  The capacitor 145 having a predetermined capacitance is sufficient to adjust the resistance value of the variable resistor 146 as described above, and is replaced with a capacitor having a different capacitance. Because it is troublesome.

  As described above, the VCO circuit block outputs a drive pulse having a cycle (frequency) corresponding to the drive cycle data Tx received from the drive signal generation circuit 223.

  Next, the rate multiplier circuit block will be described. The 16-bit register 139 stores drive cycle data Tx input via the gate 138. The rate multiplier circuit 140 reads the driving cycle data Tx from the 16-bit register 139, converts it into a rate value corresponding to the clock cycle from the CPG 232, and stores it.

  In the present embodiment, as described above, the clock frequency is 20 MHz, and the minimum unit of the rate value is 50 nS. Therefore, for example, when the cycle of the drive cycle data Tx input through the gate 138 is 25.64 μS (39 KHz), the rate value is 25640 nS ÷ 50 nS = 0512 and the remainder is 40 nS. Therefore, the rate multiplier circuit 140 stores “0512” as a rate value when the cycle of the read drive cycle data Tx is 25.64 μS (39 KHz). That is, the remainder of 40 nS is discarded. For this reason, the drive cycle (drive frequency) instructed by the rate multiplier method includes some errors.

  Next, the rate multiplier circuit 140 divides the frequency of the clock of 20 MHz by a counter circuit (not shown), and generates each pulse with a cycle of 50 nS → 100 nS → 200 nS → 400 nS ... → ... 12800 nS → 25600 nS. Next, the rate multiplier circuit 140 generates a pulse having a period corresponding to the rate value by a synthesis circuit (not shown) based on the pulse generated by the frequency dividing process. Then, the rate multiplier circuit 140 outputs the generated pulse to the drive signal generation circuit 142 as a pulse corresponding to the drive cycle data Tx related to the input.

  For example, when the cycle of the drive cycle data Tx is 25.64 μS (39 KHz), the rate value is “512”. Output. When the rate value is “511”, the rate multiplier circuit 140 outputs a pulse having a cycle of 511 × 50 nS = 25550 nS to the drive signal generation circuit 142. The pulse having a period of 25550 nS is obtained by combining a pulse having a period of 25600 nS and a pulse having a period of 50 nS obtained by the frequency dividing process.

  When the rate value is “512”, the cycle of pulses output from the rate multiplier circuit 140 to the drive signal generation circuit 142 is 25600 nS, and this cycle corresponds to a frequency of 39.062 KHz. Further, when the rate value is “511”, the cycle of the pulse output from the rate multiplier circuit 140 to the drive signal generation circuit 142 is a cycle of 25550 nS, and this cycle corresponds to a frequency of 39.139 KHz. Therefore, in the present embodiment, the resolution when driving and controlling the ultrasonic motor 30 by the rate multiplier method is 39.139 KHz-39.062 KHz = 0.077 KHz = 77 Hz.

  As described above, in the present embodiment, the resolution when the ultrasonic motor 30 is driven and controlled by the VCO method is 6.8 Hz, and the rate multiplier method is 77 Hz. Therefore, the rate multiplier method is more suitable. The resolution in driving and controlling the ultrasonic motor 30 is lower than that in the VCO method.

  In order to increase the resolution in the rate multiplier method, a method of increasing the frequency of the clock generated by the CPG 232 or a method of generating a high frequency clock by the PLL method in the internal circuit of the motor control circuit 230 may be used. Conceivable. However, these methods increase the circuit scale of the motor control circuit 230 and the level of noise generated in the circuit 230. For this reason, in the present embodiment, the rate multiplier method is used only when the target speed is low.

  Since the value of the 16-bit register 139 takes a value in the range from “1” to “65535 (all bits 1)”, the clock frequency is 20 MHz (50 nS period) as in this embodiment. In theory, the variable range of the drive frequency in the rate multiplier method is theoretically 20,000 KHz to 305 Hz (see reference numeral 211 in FIG. 3). However, for the reasons described above, in this embodiment, the drive frequency band used in the rate multiplier method is limited to the high frequency band (low speed rotation region) as indicated by reference numeral 211a in FIG.

  The variable range 211 of the drive frequency in the rate multiplier method shown in FIG. 3 includes an initial frequency of 44 KHz when the ultrasonic motor 30 described with reference to FIG. 10 is driven to rotate at a low speed. A frequency of 38 KHz for obtaining a target rotational speed is also included. Also from this point, in the present embodiment, when the ultrasonic motor 30 is rotated at a low speed, the ultrasonic motor 30 is driven by the rate multiplier method.

  The drive pulse generation circuit 142 corrects the pulse width of the pulse output from the VCO circuit 137 or the rate multiplier circuit 140 to the pulse width specified by the CPU 231 without changing the frequency (cycle). Apply the process. The drive pulse generation circuit 142 supplies the pulse subjected to the pulse width correction process to the vibrating body 31 through the coil 29 as a drive pulse for driving the ultrasonic motor.

  In the present embodiment, the pulse width of the drive pulse supplied to the vibrating body 31 is specified from the CPU 231 to the drive pulse generation circuit 142, but the drive pulse generation circuit 142 sets the frequency of the input pulse. In response to this, the pulse width may be automatically determined.

  Next, an example of drive control of the ultrasonic motor 30 will be described based on the flowcharts of FIGS.

  The flowcharts shown in FIGS. 4 and 5 show examples of drive control of the ultrasonic motor 30 when the ultrasonic motor 30 is used as an actuator for changing the shooting direction of a monitoring camera (not shown).

  First, the CPU 231 acquires the target position (target rotation angle) and target speed (target rotation speed) of the monitoring camera from a rotation parameter determination unit described later (step S1). The target position and the target speed are parameters corresponding to, for example, a case where an image is captured while tracking a suspicious person by the monitoring camera, or a case where the shooting direction of the monitoring camera is quickly switched to a direction in which a noise is generated. In the present embodiment, the target position and target speed of the surveillance camera are determined by a parameter determination unit including an infrared sensor, a sound sensor, etc., not shown.

  However, it is also possible for the CPU 231 to determine the target position and target speed of the surveillance camera mainly based on detection signals from an infrared sensor, a sound sensor, and the like. Since the monitoring camera is rotationally driven by the ultrasonic motor 30, the target position and target speed of the monitoring camera are also the target position and target speed of the ultrasonic motor 30.

  Next, the CPU 231 gives the acquired target speed to the driving method selection unit 130 and determines whether or not the target speed is 120 ° / second or more (step S2). When it is determined that the target speed is less than 120 ° / second, the drive method selection unit 130 designates the rate multiplier method and the intermittent drive method as the drive control method of the ultrasonic motor 30 (step S3).

  In this case, as described above, the driving method selection unit 130 outputs the logic “1” signal to open the gate 138, and the driving cycle data Tx is output to the rate multiplier circuit block via the gate 138. By doing so, the rate multiplier method and intermittent driving are designated. Note that when the ultrasonic motor 30 is driven and controlled by the intermittent drive control, the ultrasonic motor 30 can function as a stepping motor, and for example, highly accurate positioning can be performed.

  Next, the CPU 231 determines whether or not the target speed is 10 ° / second or more (step S4). As a result, when the target speed is 10 ° / second or more, the CPU 231 sets the pulse width of the drive pulse to 8 μS, sets the initial frequency to 37 KHz, and sets the reference speed to 240 ° / second (step S5). ).

  In step S5, the CPU 231 sets “3” as the variable N as the predetermined number of interruptions. This prescribed number of interruptions N defines how many interruptions by the detection pulse from the encoder 224 are performed after the rotational drive of the ultrasonic motor 30 is started and before the rotational drive is stopped. . That is, the prescribed number of interruptions N defines the drive stop timing when the ultrasonic motor 30 is intermittently driven.

  On the other hand, when the target speed is less than 10 ° / sec, the CPU 231 sets the pulse width of the drive pulse to 6 μS, sets the initial frequency to 44 KHz, sets the reference speed to 60 ° / sec, “2” is set to the variable N as the number of interruptions N (step S6).

  In addition, since the process of step S5, S6 is a process in the case of performing intermittent drive control, the reference speed set in step S5, S6 is reference | standard speed> target speed as mentioned above. In addition, the setting process in steps S5 and S6 is performed by the CPU 231 supplying the above set values to the motor control circuit 230 and storing them in the parameter storage unit 234.

  When the process of step S5 or S6 ends, the CPU 231 performs intermittent drive control of steps S7 to S14. In this intermittent drive control, the CPU 231 first calculates the target time of the interrupt time interval based on the detection pulse from the encoder 224 based on the target speed, and sets it to the variable Tc (step S7). For example, in the encoder 224 used in the present embodiment, the number of interrupts corresponding to a target speed of 36 ° / second is 100 interrupts / second. Therefore, when the target speed acquired in step S1 is 36 ° / second, an interrupt occurs every 10 ms on average, and the CPU 231 sets this 10 ms as the target time in the variable Tc.

  Next, the CPU 231 instructs the timer 233 to start the timing operation and also instructs the motor control circuit 230 to start the drive control of the ultrasonic motor 30 (step S8). In this case, the motor control circuit 230 controls the drive of the ultrasonic motor 30 by the rate multiplier method based on the pulse width, initial frequency, and reference speed of the drive pulse set by the CPU 231 in step S5 or S6.

  That is, the motor control circuit 230 controls the rotational speed of the ultrasonic motor 30 so that the actual speed calculated based on the detection pulse from the encoder 224 reaches the set reference speed. In addition, when performing such motor control, the motor control circuit 230 sweeps the frequency of the drive pulse in the low frequency direction starting from the initial frequency related to the above setting, and sets the pulse width of the drive pulse. Align with the pulse width related to the setting.

  Next, the CPU 231 determines whether or not the number of interruptions due to the detection pulse from the encoder 224 has reached a predetermined number of interruptions N (step S9). As a result, when the prescribed number of interruptions N has not been reached, the CPU 231 repeats the determination process in step S9. On the other hand, when the prescribed number of interruptions N has been reached, the CPU 231 stops the drive control of the ultrasonic motor 30 by the motor control circuit 230 in order to practice intermittent drive (step S10).

  Next, the CPU 231 determines whether or not the rotation position (rotation angle) of the ultrasonic motor 30, that is, the rotation position (rotation angle) of the monitoring camera has reached the target position acquired in step S1 (step S11). ). As a result, when the target position has been reached, the CPU 231 ends the drive control of the ultrasonic motor 30.

  On the other hand, if the target position has not been reached, the CPU 231 determines whether or not the value of (prescribed interrupt number N × target time Tc) is greater than the value (timer value) counted by the timer 233. (Step S12). For example, when it is desired to operate at a target speed of 36 ° / sec, the specified interrupt count N = 3 and the target time Tc = 10 ms, and (the specified interrupt count N × target time Tc) = 30 ms. In step S12, it is determined whether or not “30 ms” is greater than the timer value.

  The timer value in step S12 indicates the actual time of one cycle of intermittent driving, and (the specified number of interruptions N × target time Tc) indicates the target cycle (target time) of one cycle of intermittent driving. Yes. Therefore, the process of step S12 means that it is determined whether or not the actual cycle of one cycle of intermittent driving is shorter than the target cycle. From another viewpoint, the process of step S12 means that it is determined whether or not the actual rotational speed of the ultrasonic motor 30 in one cycle of intermittent driving is faster than the target speed in one cycle of intermittent driving. To do.

  When CPU 231 determines in step S12 that the timer value is smaller, that is, when it is determined that the actual rotational speed of ultrasonic motor 30 in one cycle of intermittent driving is faster than the target speed in one cycle of intermittent driving. Waits until the value of (prescribed interrupt number N × target time Tc) becomes the same value as the timer value (step S13), returns to step S7, and continues intermittent drive control.

  On the other hand, if the CPU 231 determines in step S12 that the timer value is equal to or greater than the value of (the predetermined number of interruptions N × target time Tc), that is, the actual value of the ultrasonic motor 30 in one cycle of intermittent driving. When it is determined that the rotational speed is equal to or lower than the target speed in one cycle of intermittent driving, a process for increasing the rotational speed of the ultrasonic motor 30 in one cycle of intermittent driving is performed (step S14).

  In the present embodiment, as a process for increasing the rotational speed of the ultrasonic motor 30 in one cycle of intermittent driving, the pulse width of the drive pulse currently driving the ultrasonic motor 30 is increased by 1 μS, The set initial frequency is set to a low frequency of 0.5 KHz. Thereafter, the CPU 231 returns to step S7 and continues intermittent drive control.

  As a process for increasing the rotational speed of the ultrasonic motor 30 in one cycle of intermittent driving, the sweep speed of the drive frequency may be increased instead of changing the initial frequency to a low frequency. This sweep speed is a switching speed when the drive frequency is gradually switched from the initial frequency to the low frequency. For example, when the initial frequency is set to 37 KHz and a sweep speed of 100 Hz / ms is set, the drive frequency is 10 ms later. Becomes 36 KHz. When this sweep speed is changed to 200 Hz / ms, the drive frequency becomes 36 KHz after 5 ms. Therefore, by increasing the sweep speed of the drive frequency, it is possible to control to quickly reach the target rotation speed.

  Further, it is possible to increase the rotational speed of the ultrasonic motor 30 in one cycle of intermittent driving by reducing the integration gain of the integrator 221 and shortening the time interval at which the integrator 221 performs integration.

  If the drive method selection unit 130 determines in step S2 that the target rotational speed is 120 ° / second or more, the drive method selection unit 130 designates the VCO method and the continuous drive method as the drive control method of the ultrasonic motor 30 (step S15). ). Next, the CPU 231 sets the pulse width of the drive pulse to 10 μS, sets the initial frequency to 39 KHz, and sets the target speed as the reference speed (step S16).

  Next, the CPU 231 starts driving the ultrasonic motor 30 and controls the motor control circuit 230 to stop driving the ultrasonic motor 30 when the motor rotation position reaches the target rotation position (step S17). To S19). In this case, it goes without saying that the motor control circuit 230 controls the drive of the ultrasonic motor 30 by the VCO method and the continuous drive method.

  As described above, in the first embodiment, when the target speed of the ultrasonic motor 30 is low and the ultrasonic motor 30 is rotated at a low speed, the driving by the rate multiplier method that digitally determines the driving pulse. Control and intermittent drive control are performed. Therefore, even when the ultrasonic motor 30 is rotated at a low speed, the torque does not become unstable, no beat sound is generated when the motor is rotated, and the life is not shortened.

  In the first embodiment, when the target speed of the ultrasonic motor 30 is high and the ultrasonic motor 30 is rotated at a high speed, the drive control by the VCO method that determines the drive pulse in an analog manner and the continuous drive control are performed. Is doing. Therefore, even when the ultrasonic motor 30 is rotated at a high speed, the resolution of the motor drive control is not lowered, and the rotating operation is not unstable.

  In the first embodiment, the target speed for determining which of the drive control by the rate multiplier method, the intermittent drive control, the drive control by the VCO method, and the continuous drive control is selected, Although it is set to 120 ° / second, the above selection / determination can be performed at a target speed other than this.

  In step S4, parameters such as the initial frequency and the reference speed are set to different values depending on whether or not the target speed is 10 ° / second or more, but 20 ° / second, 30 ° / second, ..., it is also possible to change the value of the above parameter to small increments by discriminating in small increments of 110 ° / second.

  Further, as in steps S12 → S14, when the actual rotational speed of the ultrasonic motor 30 in one cycle of intermittent driving is equal to or lower than the target speed in one cycle of intermittent driving, the rotational speed of the ultrasonic motor 30 is only increased. Instead, the rotational speed of the ultrasonic motor 30 may be decreased when the actual rotational speed of the ultrasonic motor 30 in one cycle of intermittent driving is much higher than the target speed in one cycle of intermittent driving. .

[Second Embodiment]
FIG. 6 is a block diagram showing a configuration of a drive signal generation circuit according to the second embodiment of the present invention. The drive signal generation circuit according to the second embodiment is different from the drive signal generation circuit according to the first embodiment shown in FIG. 2 in the drive signal generation circuit according to the second embodiment. The counter 151 is used in place of the driving method selection unit 130 used in the first embodiment.

  The counter 151 is provided to determine at which timing the driving method is switched during one rotation (rotation) of the ultrasonic motor 30. That is, the counter 151 receives a prescribed number of detected pulses of the encoder 224 (hereinafter referred to as encoder setting value) from the CPU 231 and sets it as an initial counter value. The counter 151 decrements the encoder setting value by “1” every time a detection pulse (hereinafter referred to as an encoder signal) is input from the encoder 224.

  At this time, the counter 151 outputs a logic “1” signal until the counter value becomes “1”, and outputs a logic “0” signal when the counter value becomes “0”. The counter 151 stops the counting operation when the counter value becomes “0”.

  When the output of the counter 151 is “1”, the driving cycle data Tx is sent to the 16-bit register 139 through the gate 138, and the driving control by the rate multiplier method and the intermittent driving control are executed. When the output of the counter 151 is “0”, the drive cycle data Tx is sent to the VCO value calculation unit 134 via the gate 133, and drive control by the VCO method and continuous drive control are executed.

  That is, in the second embodiment, the driving method is selected in the course of a series of sweep operations in which the frequency of the drive pulse is swept to obtain the target speed. Specifically, in the second embodiment, at an initial stage where the ultrasonic motor 30 starts to rotate (stage where the rotation speed is low), the ultrasonic motor 30 is driven and controlled by the rate multiplier method and the intermittent drive method. When the ultrasonic motor 30 reaches a certain rotational speed, the ultrasonic motor 30 is driven and controlled by switching to the VCO method and the continuous drive method.

  Therefore, also in the second embodiment, it is possible to obtain the same effect as in the first embodiment. In the second embodiment, the encoder value set in the counter 151 is changed, or the resistance value of the resistor 147 of the VCO circuit 137 is changed, thereby driving the VCO more than in the first embodiment. The variable frequency range at the time of control is further narrowed to increase the control resolution, and the rotation speed at the time of high speed rotation can be further stabilized.

[Third Embodiment]
FIG. 7 is a block diagram showing a configuration of a drive signal generation circuit according to the third embodiment of the present invention. The main difference between the drive signal generation circuit according to the second embodiment and the drive signal generation circuit according to the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. In the drive signal generation circuit according to the third embodiment, the drive method is not selected by the drive method selection unit 130 and the counter 151 as in the first and second embodiments, but by the signal from the CPU 231. The driving method is selected.

  In the first and second embodiments, the VCO method and the rate multiplier method are used. In the third embodiment, the VCO method is used, but the rate multiplier method is not used. Also features.

  That is, the CPU 231 sets the logic of the P0 signal to “0” when the ultrasonic motor 30 is driven at a low speed. The P0 signal of “0” is inverted by the inverter 155 and input to the gate 138 as a signal of “1”, and the gate 138 is opened. As a result, the driving cycle data Tx is output to the low speed VCO value calculation unit 157 via the gate 138.

  Further, when driving the ultrasonic motor 30 at high speed, the CPU 231 sets the logic of the P0 signal to “1”. The P1 signal of “1” is input to the gate 133 and the gate 133 is opened. As a result, the driving cycle data Tx is output to the high speed VCO value calculation unit 156 via the gate 133.

  The Tmax and Tmin used in the low speed VCO value calculation unit 157 have values corresponding to the drive frequency band 213 shown in FIG. 8, and the low speed VCO value calculation unit 157 performs drive control during low speed rotation. The VCO value is calculated. Further, Tmax and Tmin used in the high-speed VCO value calculation unit 156 have values corresponding to the drive frequency band 212 shown in FIG. 8, and the high-speed VCO value calculation unit 156 performs drive control during high-speed rotation. The VCO value for performing is calculated. A method for setting the above Tmax and Tmin will be described later.

  The VCO value calculated by the low-speed VCO value calculation unit 157 or the high-speed VCO value calculation unit 156 is stored in the 10-bit register 135, converted to an analog voltage by the DA conversion circuit 136, and output to the VCO circuit 137. Is done.

  When an analog voltage corresponding to the VCO value is input, the VCO circuit 137 outputs a pulse having a period corresponding to the analog voltage as described in the first embodiment. The output period (frequency) can be adjusted by the variable resistor 146 and the capacitor 145. As in the first and second embodiments, in the third embodiment, continuous driving is performed when the ultrasonic motor 30 is driven by the VCO method.

  In the third embodiment, a fixed resistor 158 is connected in series between the CPU 231 and the variable resistor 146. The fixed resistor 158 receives a P1 signal from the CPU 231. The middle point of the fixed resistor 158 and the variable resistor 146 is connected to the CPU 231, and the P2 signal from the CPU 231 is input to this middle point.

  When the P1 signal is at the GND level and the P2 signal is in the open state, the range of the driving frequency band 213 on the low frequency side shown in FIG. 8 is determined by the resistance values of the variable resistor 146 and the fixed resistor 153.

  When the P1 signal is open and the P2 signal is at the GND level, the range of the driving frequency band 212 on the high frequency side shown in FIG. 8 is determined by the resistance value of only the variable resistor 146.

  For this reason, even if the VCO circuit 137 receives a signal of the same voltage level from the DA converter circuit 136, the frequency of the pulse output from the VCO circuit 137 changes depending on the states of the P1 and P2 signals.

  When the P0 signal is logic “1”, the CPU 231 has the P1 signal at the GND level and the P2 signal open, and when the P0 signal is at the logic “0”, the P1 signal is open and the P2 signal is at the GND level. It is controlled to become.

  As described above, in the third embodiment, by selecting one of the high speed VCO value calculation unit 156 and the low speed VCO value calculation unit 157 by the control signals P0, P1, and P2 from the CPU 231, the low frequency Driving pulses having driving frequencies in two frequency bands on the high frequency side and the high frequency side are individually generated.

  Therefore, when the motor control circuit 230 does not include a circuit for generating a drive pulse by the rate multiplier method, even if the drive control is performed from the low speed rotation to the high speed rotation by the VCO method, the resolution of the control by the VCO method is lowered. In this case, it is possible to prevent the rotational speed from becoming unstable and increasing noise during high-speed rotation.

  The present invention is not limited to the first to third embodiments described above. For example, when the ultrasonic motor is driven and controlled by the rate multiplier method, the intermittent drive control is not necessarily performed. Continuous drive control may be performed. Moreover, it can be used not only for rotating the surveillance camera but also for other purposes such as automatic focusing of the camera and robot.

It is a block diagram which shows schematic structure of the drive control part of the vibration type actuator (ultrasonic motor) in the 1st-3rd embodiment of this invention. FIG. 2 is a block diagram of a drive signal generation circuit according to the first embodiment in the drive control unit of FIG. 1. It is a figure which shows the relationship between the drive frequency and rotation speed in 1st Embodiment. It is a flowchart which shows the motor drive control example in 1st Embodiment. FIG. 5 is a flowchart continued from FIG. 4. FIG. 6 is a block diagram of a drive signal generation circuit according to a second embodiment. FIG. 10 is a block diagram of a drive signal generation circuit according to a third embodiment. It is a figure which shows the relationship between the drive frequency and rotation speed in 3rd Embodiment. It is a schematic diagram for demonstrating the outline | summary of the drive control of an ultrasonic motor. It is a figure for demonstrating the relationship between a drive frequency and a rotational speed. It is a schematic diagram which shows the vibration wave of the stator surface at the time of high speed rotation and low speed rotation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 ... Ultrasonic motor 130 ... Drive method selection part 137 ... VCO circuit 140 ... Rate multiplier circuit 151 ... Counter 146 ... Variable resistor 156 ... High speed VCO value calculation part 157 ... Low frequency VCO value calculation part 158 ... Fixed resistance 230 ... Motor control circuit 223 ... Drive signal generation circuit 224 ... Encoder 231 ... CPU
233 ... Timer

Claims (10)

In the drive device of the vibration type actuator having the drive control means for changing the motion speed of the movable body to which the vibration of the vibration body is transmitted by sweeping the frequency of the drive signal supplied to the vibration body,
The drive control means includes a selection means for controlling a plurality of drive means and selecting one or more drive means from the plurality of drive means.   The plurality of driving means includes a first driving means for generating a driving signal in an analog manner, a second driving means for digitally generating a driving signal, and a third driving means for intermittently supplying the driving signal to the vibrating body. 2. The vibration type actuator driving device according to claim 1, comprising at least two of a driving unit and a fourth driving unit that continuously supplies a driving signal to the vibrating body.   3. The vibration type actuator according to claim 1, wherein the selection unit selects one or more drive units from the plurality of drive units based on a target motion speed of the movable body. Drive device.   The selection means selects at least the first drive means when the target motion speed is equal to or higher than a predetermined speed, and at least the second drive when the target motion speed is lower than the predetermined speed. 4. The vibration actuator driving apparatus according to claim 3, wherein means is selected.   5. The vibration actuator driving apparatus according to claim 2, wherein when the first driving unit is selected, the selecting unit selects the fourth driving unit simultaneously. 6.   6. The drive device for a vibration type actuator according to claim 2, wherein when the second drive unit is selected, the selection unit simultaneously selects the third drive unit.   7. The apparatus according to claim 2, further comprising a changing unit that changes a parameter that defines an intermittent operation in the third driving unit when the third driving unit is selected by the selection unit. The drive device of the vibration type actuator described in 1.   3. The vibration according to claim 1, wherein the selection unit performs selection so as to switch the drive unit during a series of the sweep operations for obtaining a target motion speed of the movable body. Type actuator drive device.   The plurality of driving means include a plurality of driving means that determine a driving signal in an analog manner and have different frequency bands of output driving signals, and the selection means is based on the momentum of the movable body. 2. The vibration actuator driving apparatus according to claim 1, wherein at least one driving means is selected from the plurality of driving means. In a driving method of a vibration type actuator having a drive control step of changing a motion speed of a movable body to which vibration of the vibration body is transmitted by sweeping a frequency of a drive signal supplied to the vibration body,
The drive control step includes a selection step of controlling a plurality of drive means and selecting one or more drive means from the plurality of drive means.

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